[en] Ultraviolet mutagenesis follows a relation, part of which is an induction process, very similar to the induction process for induced radioresistance and induced inhibition of postirradiation DNA degradation. The repair of single-strand breaks produced by gamma rays takes place more rapidly than does postirradiation DNA degradation. Repaired DNA is degraded and there is good repair of single-strand breaks in lex cells followed by degradation of the repaired DNA. The signal for the start of radiation-induced DNA degradation is probably NOT single-strand breaks. The dose-response relation for lambda induction requires more dose and has kinetics different from those for the induction of other phenomena. We find no evidence of induced radioresistance in two lambda lysogens of E. coli. There IS induced radioresistance if the lysogens are of induction-minus phage. UV given at -79⁰C, which is believed to produce DNA-protein crosslinks, is an excellent inducer and also a good mutagen. Near UV produces lesions which are recognized by the induced repair system. At the same time, near UV also damages the induced repair system. There is increased mutagenesis at 313 nm wavelength following induction by ionizing radiation. It is likely that the phenomenon of induced radioresistance can be produced in one of several nuclei and that this one can give rise to a resistant colony. We find no evidence of induced radioresistance, nor of inhibition of postirradiation DNA degradation, in two strains of Pseudomonas

[en] Results of studies on the effects of irradiation on Escherichia coli showed that error-prone repair mutagenesis can be induced by ionizing radiation and uv light; induced single-strand DNA break repair has been confirmed and its characterization is in process; and there is clearly a separation between the induction of lambda and other phenomena. The dose-effect relationship differs and the phenomenon of radioresistance is removed. The action spectra for uv induced mutagenesis was plotted

[en] Progress is reported on the following research projects: effects of blocking DNA synthesis by hydroxyurea on induction of lambda phage; dose response curves for uv and ionizing radiation with radiosensitive and radioresistant strains of phage; effects of oxygen, rifampin, and hydrogen peroxide on induction of radioresistance; radioinduced degradation of DNA; and induction of repair system of mutagenesis with uv and ionizing radiation. (U.S.)

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[en] Progress is reported on studies on the basic aspects of radiation effects on microorganisms. Results are included from studies on the effects of uv pretreatment on the survival of γ-irradiated micrococcus luteus and uv-induced radioresistance to bacteriophage

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[en] Progress is reported on the following research projects: coordinate induction of mutagenesis, radioresistance, and inhibition of post-radiation DNA degradation; radioinduced filamentation; action spectrum for induction of K12 lambda phage; effects of uv radiation on cells in the frozen state; dependence of mutagenesis on wavelength of uv; and w-reactivation of x-irradiated phage lambda

No abstract available